Displays can be created from an array of light emitting devices each controlled by individual circuits (i.e., pixel circuits) having transistors for selectively controlling the circuits to be programmed with display information and to emit light according to the display information. Thin film transistors (“TFTs”) fabricated on a substrate can be incorporated into such displays. TFTs fabricated on poly-silicon tend to demonstrate non-uniform behavior across display panels and over time. Some displays therefore utilize compensation techniques to achieve image uniformity in poly-silicon TFT panels.
Compensated pixel circuits generally have shortcomings when pushing speed, pixel-pitch (“pixel density”), and uniformity to the limit, which leads to design trade-offs to balance competing demands amongst programming speed, pixel-pitch, and uniformity. For example, additional lines and transistors associated with each pixel circuit may allow for additional compensation leading to greater uniformity, yet undesirably decrease pixel-pitch. In another example, programming speed may be increased by biasing or pre-charging each pixel circuit with a relatively high biasing current or initial charge, however, uniformity is enhanced by utilizing a relatively low biasing current or initial charge. Thus, a display designer is forced to make trade-offs between competing demands for programming speed, pixel-pitch, and uniformity.
Displays configured to display a video feed of moving images typically refresh the display at a regular frequency for each frame of the video feed being displayed. Displays incorporating an active matrix can allow individual pixel circuits to be programmed with display information during a program phase and then emit light according to the display information during an emission phase. Thus, displays operate with a duty cycle characterized by the relative durations of the program phase and the emission phase. In addition, the displays operate with a frequency that is characterized by the refresh rate of the display. The refresh rate of the display can also be influenced by the frame rate of the video stream. In such displays, the display can be darkened during program phases while the pixel circuits are receiving programming information. Thus, in some displays, the display is repeatedly darkened and brightened at the refresh rate of the display. A viewer of the display can undesirably perceive that the display is flickering depending on the frequency of the refresh rate.